1. Field of the Invention
The disclosure relates generally to power conversion systems and methods for converting direct current power at a DC bus into alternating current power to feed an electrical system.
2. Description of the Prior Art
Solar power is an important renewable energy source that has attracted a lot of attention in recent years. However, solar power remains expensive as compared with other sources of electricity. Thus, devices such as maximum power point tracking (MPPT) circuits are used to extract the maximum amount of power from solar power generation systems.
A typical solar power generation system includes a solar power source, a DC bus for receiving direct current power from the solar power source, and a line side converter for converting the direct current power at the DC bus into alternating current power for feeding a utility or grid. The solar power generation system also includes a power conversion control system for controlling operation of the power conversion. One of the most important control objectives of the power conversion control system is to maintain the DC voltage (Vdc) of the DC bus at a certain level. One conversion control strategy for controlling the DC voltage is to control the MPPT circuit according to a measured DC voltage feedback signal (Vdc—feedback). When the DC voltage feedback signal is too high, the solar power source may be regulated to output less power. However, when the DC voltage feedback signal is too low, if the solar power source is working at about the maximum power output, it is difficult to extract more power to increase the DC voltage. Accordingly, many solar power generation systems either operate slightly below the maximum power output (resulting in less cost effective power production) or use additional energy storage for maintaining the DC voltage (resulting in additional equipment cost).
There is a need in the art to provide an improved method and system for maintaining the DC voltage which differs from conventional methods or systems and addresses one or more of the above discussed problems.